The human prostaglandin (PG) synthases, cyclooxygenase-1 and -2, (COX-1 and COX-2) are the targets of aspirin and other non-steroidal antiinflammatory drugs (NSAIDs). These two enzymes are subject to intensive study in terms of their structure-function and their mechanisms of catalysis and inhibition. The recent development of COX-2 selective inhibitors has emphasized the importance of understanding subtle facets of the functioning of the two enzyme types. An important aim of parent grant GM-53638 is to explore the mechanistic basis of COX catalysis. The central theme of this Competitive Supplemental Application involves study of novel non-mammalian COX enzymes whose characterization will provide new perspectives with which to help understand the mechanisms and reactions of the human PG synthases. In collaboration with Dr Brash, P.1. of GM-53638, collaborator Dr Nigulas Samel of Tallinn Technical University (Estonia) has recently cloned and expressed COX enzymes with differing reaction specificities from two prostaglandin-containing corals. These are the only non-vertebrate COX enzymes to have been characterized and they may be prototypical of ancestral COX enzymes. The coral COX enzymes have unique features in their oxygenase active sites, in their peroxidase active sites, in their pattern of glycosylation. The aims of this Supplemental Application are to investigate the following aspects of the coral COX with comparison and contrast to the mammalian enzymes: 1) Comparison and contrasts of the catalytic and inhibitor profiles of recombinant coral COX with mammalian COX isozymes, 2) Control of the oxygenation stereospecificity at C-15 in cyclooxygenase catalysis, 3) Analysis of the basis for the unusually low peroxidase activity of the coral COX and its impact on sparking the oxygenase reaction, and 4) Effect of glycosylation pattern on the catalytic activity of cyclooxygenases Our study of the coral COX enzymes has already spurred the discovery of novel facets of control of COX catalysis, and this Competitive Supplement application aims to extend this into further new insights stemming from the use of the coral COX as research tools. These studies will develop new insights into the biochemistry of mammalian cyclooxygenases and as a consequence have practical benefits in development of therapeutics.